The Most Complete Tyrannosaur Fossil In The Southwestern US Has Been Found


Jonathan O'Callaghan

Senior Staff Writer

Mark Johnston/NHMU

Archaeologists have found the most complete tyrannosaur fossil ever in the southwestern US, dating back 76 million years.

The species is Teratophoneus curriei, and is thought to have been one of the first tyrannosaurs to walk across North America during the Late Cretaceous Period. That dates back 90 to 66 million years ago, when the age of the dinosaurs was brought to an end by an asteroid impact.


It was found in July 2015 by Dr Alan Titus, a palaeontologist at the the Bureau of Land Management's Grand Staircase-Escalante National Monument (GSENM) in the Kaiparowits Formation in southern Utah. It’s thought this tyrannosaur was buried in a river channel or by a flooding event, which has kept it remarkably intact.

This particular finding appears to be a young adult, about 12 to 15 years old. It measures 5.2 to 6.1 meters (17 to 20 feet) long, and it has a shorter head than northern tyrannosaurs. What was particularly impressive, though, is that three-quarters of this creature’s bones were preserved. This includes the skull, which is nearly complete.

"With at least 75 percent of its bones preserved, this is the most complete skeleton of a tyrannosaur ever discovered in the southwestern US," said Dr Randall Irmis from the University of Utah in a statement. "We are eager to get a closer look at this fossil to learn more about the southern tyrannosaur's anatomy, biology, and evolution."

The bones were covered in plaster before being taken out of the rock to prevent cracking. Mark Johnston/NHMU

Between 2,000 and 3,000 people helped excavate the site, taking at least 10,000 hours to prepare the specimen for research. Following a three-week excavation in May 2017, the specimen was airlifted out. It will be kept at the Natural History Museum of Utah.


Little has been known about tyrannosaurs in the southern US until now because most have been found in the Great Plains in the northern US and Canada. This discovery should help palaeontologists work out the history of tyrannosaurs in the South.

The team are not yet sure if this species is new, or an individual of Teratophoneus. They hope to find out by looking at the size of the fossil, its growth pattern, and its biology. This will tell them how it moved, how fast it could run, and how it ate.

“The possibilities are endless and exciting,” said Irmis.

Mark Johnston/NHMU


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